Improvement in mariners  compasses



J. 3. PENDER.

' Mariner's Compass. No. 44.451. Patented Sept. 27, 1864.-

88 See N. PEIERS. Vbo wlilhngrapbnr. wamm mn, D. C.

UNITED STATES PATENT OFFICE.

J0. s. FENDER, on NEW YORK, N. Y.

IMPROVEMENT IN MARINERS COMPASSES.

Specification forming part of Letters Patent No. 44,451 dated September 27, 1864; antedatcd September 19, 1864.

To all whom it may concern:

Be it known that I, J0. S. PENDER, of New York city, of the county of New York, in the State of New York, have invented certain new and useful Improvements in Compasses; and 1 do hereby declare that the following is a full and exact description thereof, reference being had to the accompanying drawings, making part of this application.

My invention relates to a novel method of constructing a mariners compass, and has for its object to isolate the magnetic needle from all local attraction and still to preserve the polarity ot' the magnetic needle intact.

To this end rnyinvention consistsin suspending the magnetic needle in a horizontal plane passing through the center of a hollow globe or sphere, the extremities of the magnetic nee dle being equidistant from the spherical body that surrounds it. The attraction of this body is thus equalized, and hence the polarity of a magnetic needle thus suspended remains intact,while all attraction from withoutis arrested by the interposition ofthe metallic substance of which the globe is composed, and hence local attraction is entirely out off and the magnetic needle maintains its true polarity and is not in the least atfected by surrounding objects, as hereinafter more fully explained.

To enable those skilled in the art to make and use my invention, I will proceed to describe the construction and operation of my improved compass, referring by letters to the accompanying drawings, in which Figure l is an elevation of my improved compass. Fig. 2 is a top view of the same. Fig. 3 is a vertical section at the line X X, showing the internal fixtures in elevation; and Fig. 4 is a horizontal section at the line y y.

In the several figures the same letter of reference indicates the same part of the apparatus.

A is a hollow globe or sphere,which is made of iron tinned, and which will obstruct the passage of all localattraction or magnetic currents. From the lowermost portion of the interior of this globe (as it is hung in the ordinary rings) projects upward a vertically-arranged acute cone or stand, B, from the apex of which rises a small vertical shaft, 0. The upper end of thisshaftisformed into a needle-point, on which 4 point the magnetic needle of the compass is suspended, as will be presently described.

D is the magnetic needle, the form of which is clearly shown. It is constructed with two vertical and parallel posts or small columns, a a, projecting from its upper surface at its circular or annular portion (see Fig. 4) and equidistant from its center. The two posts or sleuder columns a a are connected at their upper ends by a cross bar or piece, Z), in the under or lower face or side of which is formed a disk-like cavity for the reception of the pointed end of the vertical rod. or shaft (J. From the upper surface of the portion I and vertically coincident with the point which rests on the end of. rod 0, there extends upward a vertical rod, E, on which is permanently arranged the dial F. This dial is constructed after the usual method, and isaranged on the rod E in a horizontal plane and concentric with said rod, and at such an elevation on said rod as to admitofits turning'freely (with the rod E) just beneath the glass disk G, which is inserted in the annular rim or flange H, as clearly seen at Fig. 3.

I have drawn the several figures to a scale of one-half full size, so that the drawings will give a correct idea of the relative sizes of the parts and their proportions; but it will be understood that both the form and size of the several parts may be varied without departing from the spirit of my invention, which lies in theidea ofsuspending theneedle centrally within a hollow sphere made of iron tinned, thus equalizing the attraction within said sphere, while it cuts off, deflects, obsorbs, or destroys all influence ofall local attraction orinfluence, so that the latter shall be perfectly isolated from all outward objects and tendencies to deflect itfrom its trueposition or affectits polarity. Many attempts have been made previous to my invention to improvethe ordinary compass to such a condition that its needle should not be affected by local sources of attraction or magnetism, and a compass has been made in which the needle was hung near the upper edge of a hollow hemisphere; butin this method of construction the needle is materially affected from local causes. I have discovered that a magnetic needle hung in the center of an isolating-sphere will not be at all affected by any local attraction, no matter how strong one exists, and have devised a means by which the attraction within the sphere is equalized, and the movements of the magnetic needle within this isolating-sphere may be imparted to a dial arranged so far from the center of the sphere as to be subject to ready inspection, and have thus accomplished the great desideratum so long; desired but never before obtained.

I am aware that a magnetic needle has been hung in a hemisphere; but in such a construction of compass any change in the relative positions of the needle and hemisphere by which either end of theneedle would be thrown above or out of the plane bounding the hemisphere caused the attraction between the other end and the hemisphere to be so much stronger as to exert a perceptible and disadvantageous tendency to retain the needle in an improper position and partially destroy its polarity.

I do not claim intercepting local attraction by the screening influence of iron surrounding the magnetic needle, or nearly so; but

I claim suspending the needle in the manner described within a spherically-form ed case of iron hung as set forth, said case having an opening at top sufficiently large to display the compasscard and to permit the earths action upon the needle, all as set forth.

In testimony whereof I have hereunto set my llgld and affixed my seal this 2d day of March, 1 4:.

J0. s. FENDER. [L. s.]

In presence of- J. N. MGINTIRE, DAVID J. RAMSEY. 

